Pinna cretacea ( Schlotheim, 1813 )

Seeling, Jens & Bengtson, Peter, 2003, The bivalve Pinna cretacea (Schlotheim, 1813) from the Cretaceous of Brazil, Acta Palaeontologica Polonica 48 (3), pp. 475-480 : 477-479

Pinna cretacea ( Schlotheim, 1813)

Fig. 4A–C .

Pinnites cretaceus Fauj. ; Schlotheim 1813: 113.

Pinna decussata nobis ; Goldfuss 1837: 166, pl. 128: 1, 2.

Pinna arata, Forbes ; Stoliczka 1871: 384, pl. 24: 5, pl. 25: 1, pl. 26: 5. P. cretacea Schloth. ; Geinitz 1875: 54, pl. 14: 2, 3.

P. decussata Goldf. ; Geinitz 1875: 53, pl. 15: 2, 3, pl. 16: 1.

Pinna cretacea Schlotheim ; Wegner 1905: 157, 156.

Pinna decussata Goldfuss ; Pervinqui è re 1912: 130.

Pinna cf. decussata Goldfuss ; Rennie 1930: 174, text−figs.2, 3, pl. 19: 9. Pinna cretacea Schloth. sp.; Andert 1934: 88–90.

Pinna decussata Goldfuss ; Stchepinsky 1942: 21, 55, pl. 4: 3.

Pinna decussata Goldfuss ; Dartevelle et al. 1957: 68, pl. 9: 1a–c.

Pinna aff. P. decussata Goldfuss ; Brito 1967: 7, 8, pl. 1: 7–9.

Pinna decussata ; Križ and Soukup 1975: 47–49, pl. 2: 1–5.

Pinna cretacea (v. Schlotheim, 1813); Abdel−Gawad 1986: 140, 141, pl. 30: 1; with extensive synonymy for northern and eastern European occurrences.

Material.— 37 internal moulds of the anterior end of the shell, from eight localities in the Cenomanian (Cruzes 16: no. C380.6), lower Turonian (Laranjeiras 21: no. C61.38; Laranjeiras 22: no. C62.38; Pedra Furada 5: no. C96.4), upper Turonian (Mata 10: nos C367.3, 4, 39), upper Turonian or lower Coniacian (Cajaíba 7: nos C37.7, 8, 17, 18, 55, 129–133, 189–192, 588, 598, 716–720; Mucuri 7: nos. C26.4, 5, 14, 15, 51, 53, 77, 78; Mucuri 9: no. C32.1) of the Cotinguiba Formation, Sergipe Basin, Brazil (specimen numbers prefixed by GPIH−BR) .

Description.—Large, maximum length of preserved, anterior part 250 mm; equivalve, narrow, very elongate, triangular, wedge−shaped shell; dorsal margin straight to slightly concave, ventral margin straight to slightly convex; median carina running from umbo towards posterior margin dividing valves into two nearly equal parts; each part covered with six to nine strong radial ribs separated by broad interspaces, in some specimens posterior portions of dorsal part with weaker intercalary ribs; radial ribs crossed by concentric growth lines forming net−like structure on internal moulds, strong ridges or folds near postero−ventral margin, forming acute angle with last radial rib and curving slightly towards the umbo; internal nacre divided medially into two lobes; cross−section of valves quadrate near the umbo, rhombic to diamond−shaped at midlength and flattened, lenticular towards the posterior end. Fragments of shell material is preserved in ten specimens (nos C26.14, 15, 77, 78; C37.8, 131, 133, 192, 598; C62.38).

Discussion.—Most of the European Upper Cretaceous pinnids have been assigned to Pinna cretacea ( Schlotheim, 1813) or Pinna decussata Goldfuss, 1837 . The main distinguishing character between these species is the more elongate shape of P. cretacea and its less distinctly curved ridges on the ventral part of the shell. However, their morphological differences are minor and have never been clearly defined ( Dhondt 1987). Also in Recent Pinna there is considerable variation in the width of the shell between different localities and even within the same area (C.A. Richardson, Anglesey, written communication, 2002). Moreover, most European Cretaceous pinnids are poorly preserved and commonly deformed. The width of the shell is therefore not a useful taxonomic character. The two species were synonymised by Wegner (1905), a view followed by a number of subsequent authors (e.g., Andert 1934; Abdel−Gawad 1986; Dhondt 1987) and also by us. There are also less elongate, broader specimens in the Sergipe material but the difference in shape is probably a result of post−depositional deformation. Thus, all specimens from Sergipe are assigned to P. cretacea .

P. arata Forbes, 1846 was originally based on the presence of secondary ribs on the dorsal part of the shell. In all other respects it is similar to P. cretacea , as already discussed by Stoliczka (1871). Secondary ribs are also seen in some of the specimens from Sergipe and we consider this feature to fall within the variability of P. cretacea .

The North American species Pinna laqueata Conrad, 1858 (see Stephenson 1955) and Pinna calamitoides Shumard, 1858 (see Packard and Jones 1965) closely resemble P. cretacea . This applies to their general outline and ornamentation as well as to the internal characteristics of the shell ( Abdel−Gawad 1986).

Atrina laticostata ( Stoliczka, 1871) is a very similar species described from the Albian to Campanian of West Africa ( Nigeria, Gabon, Cameroon) (e.g., Solger 1904; Riedel 1932; Dartevelle et al. 1957; Barber 1958) and southern India ( Stoliczka 1871). It is differentiated from P. cretacea by having fewer ribs and by the lack of a median carina. In all other respects the species are similar and poorly preserved specimens may be easily confused.

Atrina reginamaris ( Maury, 1930) from the Maastrichtian of the Pernambuco−Paraíba Basin is distinguished by its broader posterior end, more concave dorsal margin and more convex ventral margin, its smaller number of radial ribs, which are separated by much broader interspaces, and by the absence of a nacreous inner layer ( Fig. 4D ).

Occurrence.—Widely distributed in the Albian to Maastrichtian of Europe, Africa and southern India; in Brazil the species occurs in the Albian of the Camamu Basin and the Cenomanian to lower Coniacian of the Sergipe Basin.

Figures

Fig. 4. Pinna cretacea (Schlotheim, 1813) from Sergipe. A. Right valve (no. GPIH−BR C37.192), from Cajaíba 7, Cotinguiba Formation, upper Turonian or lower Coniacian. B. Right valve, internal mould with trace of bilobate internal nacreous layer (no. GPIH−BR C26.14), from Mucuri 7, Cotinguiba Formation, upper Turonian. C. Pinna cretacea (Schlotheim, 1813) from Sergipe; internal moulds of two left valves preserved in life position (nos GPIH−BR C37.716, 717), from Cajaíba 7, Cotinguiba Formation, upper Turonian or lower Coniacian. D. Atrina reginamaris (Maury, 1930) from the Pernambuco−Paraíba Basin (no. DG−CT−UFPE 3232), from “Pedreiras do Roger”, João Pessoa, Paraíba (“locality 5” of Muniz 1993), Gramame Formation, Maastrichtian; specimen housed in the collections of the Department of Geology of the Universidade Federal de Pernambuco, Recife, Brazil. Scale bars 2 cm.